Table 19.1 Summary of Molecular Probes fluorescent Ca2+ indicators.

Ca2+ Indicator Water-Soluble Salt * Cell-Permeant Ester † Dextran ‡ Mode § Kd (nM) ** Notes
Bis-fura-2B6810  Ex 340/380
370
1
BTCB6790B6791 Ex 400/480
7000
2
Calcium Green-1C3010MPC3011MP, C3012C6765, C3713, C3714Em 530
190
3, 4
Calcium Green-2C3730C3732 Em 535
550
3, 5
Calcium Green-5NC3737C3739 Em 530
14,000
3
Calcium OrangeC3013C3015 Em 575
185
2
Calcium Crimson C3018 Em 615
185
2
Fluo-3F1240, F3715F1241, F1242, F14218, F14242, F23915 Em 525
390
3, 4
Fluo-4F14200F14201, F14202, F14217, F23917 Em 520
345
3
Fluo-5FF14221F14222 Em 520
2300
3
Fluo-4FFF23980F23981 Em 520
9700
3
Fluo-5NF14203F14204 Em 520
90,000
3
Fura-2F1200, F6799F1201, F1221, F1225, F14185F3029Ex 340/380
145
2
Fura-4FF14174F14175 Ex 340/380
770
2
Fura-6FF14178  Ex 340/380
5300
2
Fura-FFF14180F14181 Ex 340/380
5500
2
Fura RedF14219F3020, F3021 Ex 420/480
140
2, 6
Indo-1I1202I1203, I1223, I1226 Em 405/485
230
2
Mag-fluo-4M14205M14206 Em 520
22,000
3
Mag-fura-2M1290M1291, M1292 Ex 340/380
25,000
2
Mag-indo-1 M1295 Em 405/485
35,000
2, 7
Magnesium GreenM3733M3735 Em 530
6000
3
Oregon Green 488 BAPTA-1O6806O6807O6798Em 520
170
3
Oregon Green 488 BAPTA-2O6808O6809 Em 520
580
3, 8
Oregon Green 488 BAPTA-6FO23990  Em 520
3000
3
Oregon Green 488 BAPTA-5NO6812  Em 520
20,000
3
Quin-2Q23918  Em 495
60
2, 9
Rhod-2R14220R1244, R1245MPR34676 ††Em 580
570
3, 10
Rhod-3 R10145 Em 580
570
3
Rhod-FF R23983 Em 580
19,000
3
Rhod-5NR14207  Em 580
320,000
3
X-rhod-1 X14210 Em 600
700
3
X-rhod-5FX23984X23985 Em 600
1600
3
* Catalog number(s) for the cell-impermeant salt. † Catalog number(s) for the cell-permeant AM ester. ‡ Catalog number(s) for the dextran conjugates. § Measurement wavelengths, in nm, where Ex = fluorescence excitation and Em = fluorescence emission. Indicators for which a pair of wavelengths are listed have dual-wavelength, ratio-measurement capability. ** Ca2+ dissociation constant, measured in vitro at 22°C in 100 mM KCl, 10 mM MOPS, pH 7.2, unless otherwise noted. Kd values depend on temperature, ionic strength, pH and other factors, and are usually higher in situ. Because indicator dextrans are intrinsically polydisperse and have variable degrees of substitution, these values may vary; lot-specific Kd values are printed on the vial in most cases. †† High-affinity dextran conjugate.

1. Ca2+-dependent fluorescence response similar to fura-2 but ~75% greater molar absorptivity. 2. The AM ester form is fluorescent (a major potential source of error in Ca2+ measurements). 3. The AM ester form is nonfluorescent. 4. Calcium Green-1 is more fluorescent than fluo-3 in both Ca2+-bound and Ca2+-free forms. The magnitude of the Ca2+-dependent fluorescence increase is greater for fluo-3; see Fluorescent Ca2+ Indicators Excited with Visible Light—Section 19.3. 5. Larger Ca2+-dependent fluorescence increase than Calcium Green-1. 6. Can also be used in combination with fluo-3 for dual-wavelength ratio measurements, Ex = 488 nm, Em = 530/670 nm ref. 7. Kd determined in 100 mM KCl, 40 mM HEPES, pH 7.0 at 22°C ref. 8. Larger Ca2+-dependent fluorescence increase than Oregon Green 488 BAPTA-1. 9. Kd determined in 120 mM KCl, 20 mM NaCl, pH 7.05 at 37°C.ref 10. The Kd value for the high-affinity rhod dextran (R34676) is ~780 nM.
For Research Use Only. Not for use in diagnostic procedures.